In the preparation of chip-type snack products a thin sheet of dough, called masa in the case of corn products, is formed and cut into smaller bite-size pieces of desired configuration. The cut pieces are delivered to further processing and a frying process where the dough is typically fried in oil. Food products which can be manufactured in this manner include fabricated potato chips and chips derived from grain sources such as corn chips.
One problem which has existed in the use of rollers to form and cut thin masa pieces prior to the invention described herein resulted from the configuration of the rolls. Convex-concave roll configurations have been used in conjunction with stripper wires to form the sheet material, strip it from one roll and place it on another. Current practice in masa sheeting has employed a primary roll which is concave throughout the periphery of the surface of the roll and along a substantial portion of the length of the roll between the roll ends. The secondary roll is convex throughout the same portion of the roll and complementary to the concave portion of the primary roll so that the rolls can form a nip of constant thickness when aligned in close proximity to one another for forming sheet material. Similarly, the cutter is convex for engaging the primary roll at a position displaced from the secondary roll to cut the sheet formed between the two rolls, stripped from the secondary roll and delivered to the primary roll.
The convex-concave configuration was apparently adopted to maintain the wires in a taught disposition across the entire length of the roll, particularly for the secondary roll which is convex. When using wires to strip the sheet masa from the secondary roll, not only will they break and cause interruption of the production since the sheeter has to be shut down to replace the broken wire, but bands and grooves are employed for aiding in holding the stripper wire to the primary roll surface since the primary roll is concave. Bands and wires on the primary roll also break and cause production to be interrupted.
The cutting pattern typically employed is one in which the cut pieces may be contiguous to adjacent pieces in which case there is no waste dough or trim between the pieces for separation and reuse or other disposition. This type of cutting is referred to herein as full pattern cutting. The grooves and bands reduce the effective or useable width of the rolls particularly on "full pattern cutting."
In the preferred embodiment stripping of the sheet from the first roll so that the sheet always adheres to the second roll is insured by the manner of constructing the rolls. Thus each of the sheet-forming rolls is constructed so that gas pressure can be applied beneath the adjacent dough on the surface of the roll at an appropriate location on the path of the periphery of the roll. Thus, the sheet-forming rolls of the invention are rotated in opposite directions at approximately the same speed and deliver the dough in sheet form for cutting into smaller, sometimes contiguous pieces. The forming rolls are internally pressurized, and at designated points along the periphery, the pressure is used to force the dough sheet from a first of the rolls and to adhere to the other roll, herein referred to as the second roll, for contact with a cutting roll. Subsequently, the cut dough pieces are stripped from the second roll by a similarly selective application of gas pressure from within the roll. The cut pieces may become positioned on a conveyor and can be delivered to further processing and a frying operation. This technique avoids the use of the conventional stripping wires which frequently break and cause processing interruptions.
By employing a cylindrical configuration instead of the concave-convex rolls of commercial machines a shape which is easier and cheaper to manufacture can be employed. The axial positioning of the rolls in the cutter is not critical as it is for concave and convex rolls and cutters where differential speeds between the cutter and other rolls may result from improper alignment. Otherwise, there would be greater wear since slipping, rather than true rolling action, may exist. Thus, longer wear and longer useful life result for the cutter and primary roll of the invention. By eliminating the convex and concave configurations, and their accompanying grooves, wires and bands, a greater area of the rolls is available for production, e.g., a 162/3% increase assuming both machines operate at the same roll speed and are of the same length.
The rolls are characterized by an internal, non-rotating inner cylinder which can be internally pressurized with gas. This inner cylinder has a plenum trough extending axially along its outer surface, and the trough is connected to the hollow center of the roll by an axially-extending row of radial holes. A second cylindrical member whose inside surface fits closely about the outer periphery of the non-rotating cylinder, rotates about the latter cylinder. On its outer periphery the rotating cylinder is equipped with a multiplicity of peripherally spaced-apart, axially-extending troughs connected by axially positioned rows of holes to its inner surface which is contiguous with the outer surface of the non-rotating cylinder.
In this way the pressure in a first of the sheet forming rolls can be concentrated at a position that is more or less immediately downstream of the nip of the rolls where the sheet is formed, and thereby force the sheet against the other sheet-forming roll. The latter roll is adjacent a full-pattern cutting roll which cuts the dough sheet into pieces of desired size and shape. The cut pieces remain adhered to the roll. Pressure in the second sheet-forming roll is concentrated a short peripheral distance from the point of contact with the cutting roll to force the cut pieces off the second sheet-forming roll and toward the take-away conveyor. The pieces are then transported to other treatments such as toasting, conditioning and frying.